Substrate processing system and method

ABSTRACT

A system for processing substrates has a vacuum enclosure and a processing chamber situated to process wafers in a processing zone inside the vacuum enclosure. Two rail assemblies are provided, one on each side of the processing zone. Two chuck arrays ride, each on one of the rail assemblies, such that each is cantilevered on one rail assemblies and support a plurality of chucks. The rail assemblies are coupled to an elevation mechanism that places the rails in upper position for processing and at lower position for returning the chuck assemblies for loading new wafers. A pickup head assembly loads wafers from a conveyor onto the chuck assemblies. The pickup head has plurality of electrostatic chucks that pick up the wafers from the front side of the wafers. Cooling channels in the processing chucks are used to create air cushion to assist in aligning the wafers when delivered by the pickup head.

RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.13/672,652, filed on Nov. 8, 2012, which claims priority from U.S.Provisional Application No. 61/557,363, filed on Nov. 8, 2011, thedisclosures of which are incorporated here by reference in theirentireties.

BACKGROUND

1. Field

This Application relates to systems and methods for substrateprocessing, such as silicon substrates processing to form semiconductorcircuits, solar cells, flat panel displays, etc.

2. Related Art

Substrate processing systems are well known in the art. Examples ofsubstrate processing systems include sputtering and ion implant systems.While in many such systems the substrate is stationary duringprocessing, such stationary systems have difficulties meeting recentdemand for high throughput processing. The high throughput processing isespecially severe for processing substrates such as, e.g., solar cells.Accordingly, new system architectures are needed to meet this demand.

SUMMARY

The following summary of the invention is included in order to provide abasic understanding of some aspects and features of the invention. Thissummary is not an extensive overview of the invention and as such it isnot intended to particularly identify key or critical elements of theinvention or to delineate the scope of the invention. Its sole purposeis to present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented below.

Disclosed herein is a processing system and method that enables highthroughput processing of substrates. One embodiment provides a systemwherein substrates continually move in front of the processing systems,e.g., the sputtering target or ion implantation beam. During travel infront of the processing system the substrate is moved at one speed, andduring travel to/from load and unload positions the substrates are movedat a second speed, much higher than the first speed. This enables anoverall high throughput of the system.

Various disclosed embodiments provide a vacuum processing system forprocessing substrates, e.g., ion implanting, using two chuck arrays. Inthe described embodiments each chuck array has two rows of waferspositioned on electrostatic chuck on each array, but other embodimentmay use one or more rows. The arrays are mounted on opposite sides ofthe chamber, so that they can each have water/gas and electricalconnections without interfering with the operation of the other array.The use of at least two rows on each array enables continuousprocessing, i.e., continuous utilization of the processing chamberwithout idle time. For example, by using two rows for ion implantation,the ion beam can always be kept over one chuck array while the otherarray is unloaded/loaded and returned to the processing position beforethe processed array exits the beam.

In the disclosed embodiments, all wafers on the chuck array are loadedat the same time. Wafers come from the load lock in rows, several wafersabreast, e.g., three wafers abreast. When two rows are present on theincoming conveyor, the wafers are lift up to a pick and place mechanism.In one embodiment, the pick and place mechanism uses electrostaticchucks to hold the wafers, but other mechanisms, such as vacuum, may beused. The system may optionally include dynamic wafer locatingmechanisms for locating the wafer on the chucks with the correctalignment to assure that the processing is aligned to the wafer. Forexample, when performing ion implantation, the alignment ensures thatthe implanted features are perpendicular or parallel with the waferedges.

In one embodiment, the chuck arrays have manual alignment features thatare used during setup to make sure the direction of travel is parallelto the processing chamber, e.g., to implant mask features. In oneexample, the chuck arrays are first aligned to the implant masks byusing a camera at the mask location and features on the arrays. Theneach head on the pick and place mechanism is aligned to the mask bytransferring an alignment wafer with precision alignment features fromthe input conveyor to the chuck array. The array then moves under themask alignment camera and the angular displacement of the alignmentwafer is determined. This angular displacement is then used to adjustthe pick and place head. The steps are repeated until alignment issatisfactory. These steps create a fixed alignment. They are notdynamically controlled and varied by the system during wafer processing.

The pick and place heads may also have dynamic wafer alignment. Forexample, pawls may be used to push wafers against alignment pins whilethe wafer floats on a gas cushion. This gas cushion may be establishedby flowing gas into the chuck via the wafer cooling channels so thatthese channels serve a dual purpose. The alignment pins can be mountedon piezo stages for dynamic control of elevation, if needed.

In one specific example, an ion implant system is provided whichcomprises a vacuum enclosure, an ion implant chamber delivering an ionbeam into a processing zone inside the vacuum enclosure. First andsecond chuck arrays are configured to ride back and forth on first andsecond rail assemblies, respectively, wherein an elevation mechanism isconfigured to change the elevation of the rail assemblies between anupper position and a lower position. Each of the first and second chuckarrays have a cantilevered portion upon which plurality of processingchucks are positioned. Each of the first and second chuck assemblies isconfigured to travel on its respective rail assembly in the forwardsdirection when the respective rail assembly is in the upper position,and ride on its respective rail assembly in the backwards direction whenthe respective rail assembly is in the lower position to thereby passunder the other chuck assembly.

In the described ion implant system, a delivery conveyor belt ispositioned inside the vacuum enclosure on its entrance side, and aremoval conveyor is position inside the vacuum chamber in its exit side.A first pickup mechanism is configured to remove wafers from thedelivery conveyor and place the wafers onto the first and second chuckassemblies. A second pickup mechanism is configured to remove wafersfrom the first and second chuck assemblies and deliver the wafers to theremoval conveyor belt. A camera is provided to enable aligning the firstpickup mechanism. The camera is configured to take images of the firstand second chuck assemblies while positioned in the processing zone. Theimages are analyzed to determine the alignment of the first pickupmechanism.

The chuck assemblies are configured to travel at one speed while in theprocessing zone, and at a second speed, faster than the first speed,while traveling in the reverse or backward direction. In thisarrangement, when the rail assembly is in the upper position, the chuckassemblies may be traveling in either fast forward or slow forwardspeed, depending on the location, but always travel in the reverse fastspeed when the rail assembly is in the lower position.

Each of the first and second chuck assemblies has a plurality ofelectrostatic chucks having gas flow channels. The first and secondchuck assemblies are configured to deliver gas to the gas flow channelsso as to generate gas cushion when wafers are being loaded onto theelectrostatic chucks. Each of the first and second chuck assemblies alsohas plurality of alignment pins. Actuators may be included such that thepins may be actuated to assume an upper position for wafer alignment andthereafter assume a lower position.

Each of the first and second pickup mechanisms comprises a plurality ofpickup chucks arranged to mimic the arrangement of the processing chuckson the first and second chuck assemblies. Each of the pickup chucks hasassociated wafer alignment actuators configured to urge against thewafers during wafer alignment procedure. The wafer alignment actuatorsmay be configured to urge the wafers against alignment pins attached tothe chuck assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, exemplify the embodiments of the presentinvention and, together with the description, serve to explain andillustrate principles of the invention. The drawings are intended toillustrate major features of the exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of actualembodiments nor relative dimensions of the depicted elements, and arenot drawn to scale.

FIG. 1 is a cross-sectional schematic illustrating major parts of asystem and architecture according to one embodiment.

FIG. 2 is a top view of chuck arrays depicting a process flow tohighlight certain features of the embodiment illustrated in FIG. 1.

FIGS. 3A and 3B illustrate an embodiment of the chuck array system.

FIG. 4 illustrates an example of a system used with an ion implanter.

FIG. 5 illustrates a top view of the substrate loading according to oneembodiment, which enables accurate alignment of the wafers to thechucks.

FIG. 6 is a schematic view of a pickup chuck according to oneembodiment.

FIG. 7A illustrates a pickup chuck with the pawls open, while FIG. 7Billustrates a pickup chuck with the pawls in the close position.

FIG. 8A is a schematic illustrating an arrangement with a pickup chuckhaving pawls and a processing chuck having alignment pins, while FIG. 8Bis a side view of the arrangement of FIG. 8A.

FIG. 9 is a flow chart illustrating a process for transferring a waferonto the processing chuck.

FIG. 10 is a flow chart illustrating a process for aligning the pickuphead to the processing chamber.

DETAILED DESCRIPTION

Various embodiments disclosed herein provide a system architecture thatenables high processing throughput, especially for processes such assputtering and ion implant. The architecture enables pass-by processing,such that the substrate is being processed as it passes by theprocessing chamber. For example, the substrate can be passed under anion beam such that it is being implanted as it traverses the ion beam.In some specific examples, the ion beam is made as a wide ribbon, suchthat it can cover sections of several substrates simultaneously. Usingsuch an arrangement, several substrates can be passed under the beam,such that the substrates can be processed together simultaneously toincrease the system's throughput.

An embodiment of the inventive sputtering chamber will now be describedwith reference to the drawings. FIG. 1 illustrates part of a system forprocessing substrates using movable chuck arrays, indicated as C1 andC2, and positioned inside vacuum enclosure 100. In FIG. 1, a processingchamber 115 is served by the two movable chuck arrays; such that at alltimes at least one substrate is processed by the processing chamber. Theprocessing chamber 115 may be, for example, a sputtering chamber, an ionimplant chamber, etc., having a processing zone, indicated by arrow 145.The processing zone may be, e.g., an ion beam. By having the movablechuck arrays as illustrated in FIG. 1, the processing zone is alwaysoccupied by at least one substrate, so that the chamber is never in anidle mode, but rather is always processing at least one substrate.

In the example of FIG. 1, the substrates 102 arrive on a conveyor 130which, in this embodiment, is in vacuum. In this example, the substratesare arranged three abreast, i.e., in three rows as shown in the calloutL1 of FIG. 1. Also, in this example, each chuck array has six chucks106, arranged as a 2×3 array, as illustrated in the callout L2 ofFIG. 1. A pick-up head arrangement 105 rids on an overhead rail 110 and,in this example, picks up six substrates from the conveyorsimultaneously, and transfers them to the chuck array, here C1.

The wafer transport mechanism used to transport the wafers 102 from theconveyor 130 onto the processing chucks 106, employs one or moreelectrostatic pickup chucks 105, which are movable along tracks 110 anduse electrostatic force to pick up one or more wafers, e.g., one row ofthree wafers 102, and transfer the wafers to the processing chucks 106.The pickup chucks 105 electrostatically chuck the wafers from theirfront surface, and then position the wafers on the processing chucks106, which electrostatically chucks the wafers from their backside. Suchan arrangement is particularly suitable for processing solar cells,which are rather forgiving for handling from the front surface.

Meanwhile, chuck array C2 continuously passes the processing region 145of processing chamber 115, such that all six substrates will be exposedfor processing. The motion of the chuck arrays while traversing underthe processing region 145 is at a constant speed, referred to herein asS1. Once chuck array C1 has been loaded with substrates 102, it movesinto processing position behind chuck array C2. This move into theprocessing position is done at a speed, referred to herein as S2, whichis faster than speed S1, so that chuck C1 can be loaded and moved to bein position for processing before processing of the substrates on chuckarray C2 is completed. Chuck array C1 then moves behind chuck array C2at speed S1, so that when chuck array C2 exits the processing zone 145,chuck C1 immediately enters the processing zone 145. This condition isdepicted as situation A in FIG. 2, wherein chuck array C2 just completedprocessing and chuck array C1 enters the processing zone 145. In theposition illustrated in FIG. 2, chuck array C1 has just began enteringthe processing zone 145, for example, just started passing under theimplant beam 147. Chuck array C1 will continue to move slowly at speedS1 through the implant zone 147, e.g., at about 35 mm/sec. On the otherhand, chuck array C2 is just about to exit the coverage of the implantbeam 147.

Once chuck array C2 passes beyond the processing zone, i.e., exits thecoverage of ion beam 147, it then accelerates and moves at speed S2 tothe unloading position, depicted as situation B in FIG. 2. At this time,the front edge of chuck array C1 starts processing below the processingzone, while continuing to move at speed S1. As shown in this example,chuck array C1 is arranged such that three substrates are processedsimultaneously. Of course, more or less substrates can be processedsimultaneously, depending on the size of the processing zone 145, inthis example, the width of the ion beam 147.

When chuck array C2 stops at the unloading station, shown in broken-linein FIG. 1, an unloading pick-up arrangement 125 picks up the substratesand moves them onto conveyor 135. Chuck array C2 is then lowered andmoves at speed S2 below chuck array C1 to the load station, shown asposition C in FIG. 2. When chuck array C2 is loaded with substrates, itmoves into processing position behind chuck array C1, as shown inposition D in FIG. 2. This cycle repeats itself, such that substratesare always present in the processing zone 145.

FIGS. 3A and 3B illustrate an embodiment of the chuck array system. Inthis embodiment, each of chuck arrays C1 and C2 has six chucks, 352,357, each of which may be, e.g., an electrostatic chuck. Chuck array C1rides on tracks 350 on one side, while chuck array C2 rides on tracks355, situated in a position opposed to the tracks 350. Each of chuckarrays C1 and C2 can ride back and forth on its tracks, as indicated bythe double-headed arrow. The chuck arrays C1 and C2 can be moved ontracks using motors, stepping motors, linear motors, etc. Each of thetracks is coupled to an elevation mechanism 360, which assumes an upperposition and a lower position. During loading, processing, and unloadingthe elevation mechanism 360 is activated to have the tracks assume theupper position. FIG. 3A illustrates the condition wherein both tracksare in the upper position, such that all of the chucks are at the samelevel. However, during transfer from unloading position to loadingposition, the elevation mechanism 360 is activated to lower therespective track to assume the lower position, so that one chuck arraycan pass below the other. This is shown in FIG. 3B, wherein tracks 350assume the lower position and chuck array C1 passes below chuck arrayC2.

As illustrated in FIGS. 3A and 3B, each chuck array has a cantileveredshelf, 372, 374, upon which the chucks are assembled. Each of thecantilevered shelves has a drive assembly 373, 375, which rides on therails, and a free standing support assembly 374, 376, upon which thechucks are attached, and which is cantilevered from the respective driveassembly. When one rail assembly assumes the lower position, the freestanding support assembly of the respective chuck assembly can passbelow the free standing support assembly of the other chuck assembly.Also, as illustrated in FIG. 3, the shelves are cantilevered so thatwhen both rails are in upper position, the chucks situated on bothshelves are aligned in the travel direction, as shown by the brokenlines.

FIG. 4 illustrates an example of a system used with an ion implanter.The system illustrated in FIG. 4 is used for fabrication of solar cells.In the fabrication of solar cells, sometimes ion implantation isperformed on only selected areas of the substrate. An example for suchprocessing is selective emitter solar cell. According to the embodimentof FIG. 4, a mask (see, e.g., mask 170 in FIG. 1) is placed in the pathof the ion beam, such that only ions that pass through holes in the maskreach the substrate. FIG. 4 illustrates how the processing using themask proceeds and the cycle time using one numerical example.

In FIG. 4, the chuck array is shown in solid line and is illustrated tohave a length Lc in the direction of travel, while the mask is shown inbroken line and is illustrated to have length Lm in the direction oftravel. In this arrangement, an array of 3×2 is illustrated. Such thatthree wafers are positioned in the width direction to be processedsimultaneously. This particular mask can be used to provide even dopingon the surface of the wafers, and then enhanced doping for the contact“fingers” of the solar cell. That is, as the wafers is being transportedunder the mask, the wide opening of the mask enables a wideuninterrupted beam of ions to pass and evenly dope the surface of threewafers simultaneously. As the wafers continue to travel and come underthe “comb” section of the mask, only “beamlets” of ions are allowed topass to the wafers to thereby dope the wafers in straight lines.

The doping process continues uninterruptedly, such that the implantsource is always operational and always provides an ion beam. FIG. 4illustrates four snapshots of four states during the continuousoperation. In State 1, chuck array C2 is under the ion beam to implantthe wafers positioned thereupon. The leading edge of chuck array C1 isjust about to enter the area covered by the mask. Both arrays C1 and C2travel at slow speed S1. At State 2, ion implant of the wafer positionedon chuck array C2 is completed and the trailing edge of chuck array C2is just about to exit the area covered by the mask. Both arrays C1 andC2 still travel at slow speed S1.

Once array C2 completely exits the coverage area of the mask, duringtime t₂₃, it accelerates to speed S2 and travels to the unload station,wherein the wafers are unloaded from the array. The tracks of array C2are then lowered and array C2 travels at speed S2 under array C1 to beloaded with fresh wafers at the loading station. Once loaded, array C2again accelerates to speed S2 to a position just behind array C1, andthen slows down to travel at speed S1 behind array C1. State 3 is asnapshot of array C2 as its leading edge is just about to enter thecoverage area of the mask. Process then continues at speed S1, and, asshown in state 4, the trailing edge of chuck array C1 is about to exitthe coverage area of the mask, which defines one cycle. The process thenrepeats itself ad infinitum, so long as wafers are loaded onto thesystem.

As can be understood from the example of FIG. 4, the cycle time for onechuck array is t₁₂+t₂₃+t₃₄+t₄₁. In one example, this cycle time is about18 seconds. The processing time is the time from when the leading edgeof the chuck array enters the mask coverage, to the time the trailingedge of the array exits the mask coverage. However, the time a chuckarray travels at processing speed, i.e., S1, is longer and is shown inFIG. 4 to be t₁₂+t₂₃+t₃₄=18−t₄₁. On the other hand, FIG. 4 illustratesthat the time the chuck array travels at speed S2 and is unloaded andloaded with new wafers is t₂₃, which in one example is about 6 seconds.

As can be understood from the above, for proper ion implant at highthroughput speeds, the wafers need to be loaded onto the chucks at highalignment accuracy. However, since the wafers arrive on conveyor, it isdifficult to maintain accurate alignment. FIG. 5 illustrates a top viewof the substrate loading according to one embodiment, which enablesaccurate alignment of the wafers to the chucks. In this example sixsubstrates are aligned loaded simultaneously onto six chucks.

FIG. 5 is a top view of the pick-up head 105 of FIG. 1, having a 3×2array of electrostatic chucks 505 for simultaneously loading 6 wafers502. Each of the chucks 505 is capable of rotational alignment about anaxis, as indicated by double-arrow 590. The alignment is performed sothat the wafers are aligned to the mask, and is done prior to start ofprocessing. For example, as shown in FIG. 1, a camera 119 can bepositioned near the mask 170, so as to image the mask and the chuckarray. In FIG. 1, the pickup head can be rotationally aligned about axis190. For performing the alignment, a special alignment wafer withalignment mask can be used, so its alignment to the mask can be imagedusing camera 119. Once the alignment is set for a particular mask, thealignment stays static and need not be changed for each cycle. Inpractice, this rotational alignment is required only for the loadingpick-up head 105, and is not required for the unloading pick-up head125.

Each individual wafer is aligned to its individual processing chuck bymovable pawls 585, which push the wafer against pins 580. The pawls 585are in the open position when a wafer is picked up by the chuck 505, andthen are closed, e.g., by gravity, to press the wafers against the pins580 for alignment. The pins 580 may be fixed or may be movable by, e.g.,piezo, as will be explained below. As will be described with respect tothe example of FIG. 8, gas flow may be used to float the wafer as it isbeing aligned to the chuck.

FIG. 6 is a schematic view of a single pickup chuck of the pickup head,e.g., pickup chucks 505 of pickup head 105, according to one embodiment.As illustrated in FIG. 5, six such pickup chucks 505 can be arranged onone pickup head 105, so as to transport six wafers simultaneously. Inthe embodiment of FIG. 6, each pickup chuck has individual radialalignment about axis 690. For example, each time a new mask is installedon the ion implant system, each of the pickup chucks can be individuallyradially aligned so that when they deliver the wafers to the processingchucks, the wafers are aligned to the mask. Once alignment is completed,processing can commence and no further alignment may be required untilsuch time as a new mask is installed.

Each wafer is held by an electrostatic chuck 605, and is aligned to theprocessing chuck. In one embodiment, the wafer is aligned by havingstatic pins on two sides and movable alignment levers on the twocounter-sides. In FIG. 6 static pins 680 are fixed and are arranged suchthat one pin is centered on one side of the wafer and two pins areprovided on the adjacent side of the wafer at 90° angle. As shown inFIG. 5, the two pins are provided on the side that is the leading edgeof the wafer, i.e., the side of the wafer that is the leading edgeduring transport of the wafer. Two movable levers, in FIG. 6 two pawls685, push the wafer against the static pins so as to align the wafer.The levers may have defined point of contacts, e.g., pins or bumps, suchthat only the defined point of contact touches and urges the waferagainst the static pins. As shown in FIG. 5, some pawls have only asingle point of contact, while others may have two or more points ofcontact. In FIG. 5, the pawls that urge against the leading edge of thewafer have two points of contact 512.

FIGS. 7A and 7B illustrate an example wherein levers 780 from both sidesof the wafer urge the wafer to assume an aligned position. In FIG. 7Alevers 780 are in the open position, i.e., not urging the wafer 702. Thewafer 702 is held by electrostatic chuck 705, which is aligned aboutaxis 790. In FIG. 7B the levers 780 assume the close position and urgethe wafer to assume an aligned position.

FIGS. 8A and 8B illustrate another embodiment, wherein the alignment isperformed partly by the pickup chuck and partly by the processing chuck.In the embodiment of FIGS. 8A and 8B, the electrostatic chuck 805 isradially aligned about axis 890 and electrostatically holds wafer 802.During the time that the electrostatic chuck 805 holds wafer 802 thepawls 885 are in the open position, such that they do not urge againstthe wafer 802. When the pickup chuck delivers the wafer to theprocessing chuck 806, gas is pumped under the wafer via channels 833 inthe chuck. This creates an gas cushion upon which the wafer floats. Atthat time, the levers 855 assume the close position, e.g., by gravity oractuators, to urge the wafer against the fixed pins 880. As,illustrated, in this embodiment the fixed pins 880 are attached to thebase 874 of the chuck array, upon which processing chuck 806 is mounted.Once the levers 885 have urged the wafer against the pins 880, air flowcan be terminated and the processing chuck energized so as to chuck thewafer in an aligned position. Also, in this embodiment the pins 880 aremovable in the z-direction, i.e., elevated for alignment and loweredduring transport and processing, as illustrated by the double-headedarrow.

FIG. 9 is a flow chart illustrating a process for transferring a waferonto the processing chuck using the embodiment shown in FIGS. 8A and 8B.Similar processes can be performed using other disclosed embodiments. Inthe embodiments described above the transfer is performed from aconveyor belt onto a processing chuck, or vice versa, but a similarprocess can be performed when transferring from, e.g., a wafer cassette,a wafer tray, robot arm, etc. The process starts at step 900 by placingthe pickup head at the pick up position, over the wafer to be picked up.In step 905 the pickup head is activated to pick up the wafer by, e.g.,vacuum, electrostatic force, mechanical attachment, etc. In step 910 thepickup head is moved to the drop off position, e.g., over the processingchuck.

Since this process relates to the embodiment of FIGS. 8A and 8B, in step915 gas flow is activated, so as to flow gas through the processingchuck. This step is optional and is performed only when gas flowchannels are included in the processing chuck. Such gas channels areusually included in the chuck for the purpose of flowing cooling gas,such as helium, but the same arrangement can be used for the purpose ofcreating a gas cushion to float the wafer above the processing chuck.The gas cushion can be maintained by flowing helium, argon, nitrogen,air, etc. Also, if used, at this time the alignment pins can be elevatedto their upward alignment position.

The wafer is then released onto the gas cushion at step 920 and, as thepickup head is elevated a bit over the dropped wafer, the alignmentmechanism aligns the wafer over the chuck in step 925. The alignmentmechanism may be static pins and movable levers or pawls as illustratedin the above embodiments. In step 930 gas flow is reduced until it stopsso that the wafer can be gently lowered onto the chuck without going outof alignment, and in step 935 the wafer is chucked onto the processingchuck. This can be done by vacuum, mechanical clamping, electrostaticforce, etc. At step 940 the pickup head is moved away and, if used, thealignment pins are lowered.

FIG. 10 is a flow chart illustrating a process for aligning the pickuphead to the processing chamber. This is done to align the radialposition of the pickup head to the processing chamber, so it is doneonly if the process generates features on the wafer and wherein thealignment of the features to the wafer's topology is critical.Otherwise, this process need not be performed. Thus, for example, if theprocessing generates a uniform layer over the entire surface of thewafer, no alignment is needed. However, if the processing generatesfeatures, such as, e.g., contact fingers on a solar cell, then thealignment process may be carried out before processing commences. Afterthe alignment is done, processing may commence without the need forfurther alignment.

In Step 1000 the pickup head is moved into position and loads a wafer.If multiple pickup chucks are used, then multiple wafers can be loaded.Also, in one example, a specially designed alignment wafer(s) can beused. For example, the wafer can have special marks to assist indetermining proper alignment. At step 1005 the pickup head is moved todrop the wafer(s) onto the processing chuck(s). Then at step 1010 thechuck array is moved onto wafer processing position and at step 1015 animage of the chucks and/or wafers is taken. For example, if the systemis used for ion implantation through a mask, the image may be of themask, as aligned to the marks on the alignment wafers. At step 1020 theimage is inspected and it is determined whether the alignment is proper.If it is not, the process proceeds to step 1025 where the properalignment is performed to the pickup head. Then the process repeats toconfirm the alignment. If at step 1020 it is determined that thealignment is proper, then at step 1030 regular processing can commence.

It should be understood that processes and techniques described hereinare not inherently related to any particular apparatus and may beimplemented by any suitable combination of components. Further, varioustypes of general purpose devices may be used in accordance with theteachings described herein. The present invention has been described inrelation to particular examples, which are intended in all respects tobe illustrative rather than restrictive. Those skilled in the art willappreciate that many different combinations will be suitable forpracticing the present invention.

Moreover, other implementations of the invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the invention disclosed herein. Various aspects and/orcomponents of the described embodiments may be used singly or in anycombination. It is intended that the specification and examples beconsidered as exemplary only, with a true scope and spirit of theinvention being indicated by the following claims.

The invention claimed is:
 1. A wafer processing system, comprising: avacuum enclosure having a processing region; a processing chamberattached to the vacuum enclosure and defining a processing zone withinthe vacuum enclosure; a first rail assembly positioned inside the vacuumenclosure on one side of the processing chamber; a first elevationmechanism coupled to the first rail assembly and configured to raise thefirst rail assembly to elevated position and lower the first railassembly to lower position; a second rail assembly positioned inside thevacuum enclosure on opposite side of the first rail assembly; a secondelevation mechanism coupled to the second rail assembly and configuredto raise the second rail assembly to elevated position and lower thesecond rail assembly to lower position; a first chuck assemblypositioned and configured to ride on the first rail assembly in aforward travel direction while traversing under the processing regionwhen the first rail assembly is in the elevated position to therebyperform pass-by processing; and, a second chuck assembly positioned andconfigured to ride on the second rail assembly in a forward traveldirection while traversing under the processing region when the secondrail assembly is in the elevated position to thereby perform pass-byprocessing.
 2. The system of claim 1, further comprising a waferdelivery mechanism positioned inside the vacuum enclosure and a waferremoval mechanism positioned inside the vacuum enclosure.
 3. The systemof claim 2, further comprising a first pick-and-place assemblyconfigured to transfer wafers from the wafer delivery mechanism to thefirst and second chuck assemblies, and a second pick-and-place assemblyconfigured to transfer wafers from the first and second chuck assembliesto the wafer removal mechanism.
 4. The system of claim 3, wherein thewafer delivery mechanism comprises a first conveyor belt and the waferremoval mechanism comprises a second conveyor belt.
 5. The system ofclaim 4, wherein the pick-and-place assembly comprises a pickup headhaving a plurality of pickup chucks configured for simultaneouslychucking a plurality of wafers.
 6. The system of claim 5, wherein eachof the chuck assemblies comprises a plurality of electrostatic chucks.7. The system of claim 6, wherein the pick-and-place assembly furthercomprises actuators configured to align the wafers to the plurality ofchucks.
 8. The system of claim 7, wherein each of the chuck assembliescomprises a plurality of alignment pins configured for aligning thewafers by urging the wafers against the alignment pins.
 9. The system ofclaim 1, wherein the first chuck assembly is positioned on a firstcantilevered shelf configured to ride on the first rail assembly; and,wherein the second chuck assembly is positioned on a second cantileveredshelf configured to ride on the second rail assembly.
 10. The system ofclaim 1, further comprising a transport mechanism configured to operatesuch that when the first chuck assembly exits the processing zone, thesecond chuck assembly immediately enters the processing zone and whenthe second chuck assembly exits the processing zone, the first chuckassembly immediately enters the processing zone.
 11. The system of claim1, wherein each of the first and second chuck assemblies is furtherconfigured to ride on its respective first and second rail assemblies inthe backwards direction when the respective first and second railassembly is in the lower position, to thereby pass under the other oneof the first and second chuck assemblies.
 12. The system of claim 11,wherein each of the first and second chuck assemblies travels in thebackward direction in a speed that is faster than speed of the forwardtravel direction.
 13. The system of claim 1, wherein the processingregion comprises an ion implantation beam.
 14. The system of claim 13,wherein ion implantation beam is a wide ion beam such that it can coversections of several substrates simultaneously.
 15. The system of claim1, wherein the processing region comprises a sputtering target.
 16. Thesystem of claim 1, wherein when both first and second rail assembliesare in the elevated position, the first and second chuck assemblies arealigned in the travel direction.